Low temperature liquefied gas storage tank

ABSTRACT

A low-temperature liquefied gas storage tank comprising an outer tank made of rigid metals and an inner tank having a thin film construction. The inner tank is provided at its upstanding peripheral inside surface with vertically extending corrugations and includes means for suspending its upper peripheral edge so as to permit contraction and expansion of the inner tank when it is subjected to a liquid load or exposed to a low temperature. The inner tank prevents undesirable cracking and damage thereof and can store the low-temperature liquefied gas in a safe manner.

United States Patent I U.S.Cl

Katsuro Yamamoto Tokyo;

Kuniyoshi Obata, Kawasaki; Shinji Nakagawa, Kasukabe, Japan 777,338

Nov. 20, 1968 Mar. 1 6, l 97 1 Bridgestone Liquefied Petroleum GasCompany Limited Tokyo, Japan Inventors Appl. No. Filed Patented AssigneeLOW TEMPERATURE LIQUEFIED GAS STORAGE TANK 5 Claims, 9 Drawing Figs.

Int. Cl Field of Search 220/ 10, 9 9 14/74 (A) References Cited UNITEDSTATES PATENTS 6/1959 Morrison 2,994,452 8/1961 Morrison 220/9(A')3,085,708 4/1963 Dosker 220/9(A) 3,150,794 9/1964 Schlumberger et al.220/9(A) 3,l 50,795 9/1964 Schlumberger 220/9(A') 3,352,443 11/1967Sattelberg eta] 220/9(A') Primary Examiner-Joseph R. Leclair AssistantExaminerJames R. Garrett Attorney-Holman & Stern ABSTRACT: Alow-temperature liquefied gas storage tank comprising an outer tank madeof rigid metals and an inner tank having a thin film construction. Theinner tank is provided at its upstanding peripheral inside surface withvertically extending corrugations and includes means for suspending itsupper peripheral edge so as to permit contraction and expansion of theinner tank when it is subjected to a liquid load or exposed to a lowtemperature. The inner tank prevents undesirable cracking and damagethereof and can store the lowtemperature liquefied gas in a safe manner.

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LOW TEMFETURE LHQUEFIED GAS STORAGE TANK This invention relates to tanksfor use in storing gases such as methane, ethane, ethylene, propane inliquid state, each of which is gaseous state at room temperature underatmospheric pressure, but can be liquefied by cooling to its boilingpoint under atmospheric pressure. 7

Such low-temperature liquefied gas storage tank heretofore proposedcomprises a cylindrical inner tank having a fiat bottom portion and aspherical cover roof portion, a cylindrical outer tank provided aroundthe inner tank, and granular heat insulating material filled in a spaceformed between the inner and outer tanks, thereby forming so called adouble-walled tank. Such tank heretofore proposed makes use of granularheat insulating material such as perlite-as the heat-insulating materialso that the heat-insulating layer can be formed in a comparatively easyand less expensive manner, but has disadvantages that both of the innerand outer tanks must be made of metal, that the inner tank must be madeofv low temperature resistant material and can withstand the innerpressure produced therein, and that the low-temperature liquefied gasescould not be stored in a safe manner.

The principal object of the invention is to provide a storage tankwithout having the above-mentioned disadvantages inherent to theheretofore proposed tanks. and a tank that is highly safe in operation.

A feature of the invention is the provision of such an improved storagetank which comprises an inner tank containing low-temperature liquefiedgas and having a thin film construction whose peripheral inside surfacehas specially shaped vertically extending corrugations and means forsuspending the upper peripheral edge of the inner tank so as to permitcontraction and expansion of the inner tank when it is subjected to aliquid load or exposed to a low temperature and hence prevent crackingand damage of the inner tank owing to contraction phenomenon of theinner tank as a whole, with the result that the low-temperatureliquefied gas can be stored in a safe manner.

A liquefied gas storage tank according to the invention comprises, incombination, an outer tank having a pressuretight and hermeticallysealed construction, a heat-insulating layer having substantialresistance to compression provided in the inside surface of at leastside and bottom portions of said outer tank, and an inner tank having athin film construction and provided in the inside of saidheat-insulating layer, the pressure of the liquefied gas being supportedthrough said heat-insulating layer by said outer tank, said inner tankhaving the thin film construction being formed into a bag shaped bodyconsisting of a flat bottom plate and a side shell connected through athin film connector construction in the form of a portion of a toroid tosaid bottom plate, the upper peripheral edge of said bag-shaped innertank being connected through a longitudinally followable device to a topstructure of said outer tank, an upper opening of said inner tank beingcovered by a top cover plate secured to said top structure independentlyof said inner tank and provided at its top side with a heat-insulatinglayer, and said inner tank having vertically extending corrugationsarranged in spaced relation at the periphery of said side shell andsmoothly terminating at the neighborhood of said connector construction.

Additional objects of the invention together with the featurescontributing thereto and the advantages accruing therefrom will beapparent from the following description when read in conjunction withthe drawing, wherein:

FIG. 1 is a vertical sectional view of a storage tank according to theinvention;

FIG. 2 is a perspective view of bottom parts of the tank shown in FIG.3, in which a part is shown in a sectional view;

FIGS. 4-A and 4-B are diagrammatic cross sections through the inner tankshown in FIGS. 1 and 2 for explaining the contraction change thereof;

FIG. 5 is a front view of the outside surface of the inner tank; and

FIGS. 6, 7 and 8 are fragmentary radial cross sections showing differentembodiments of devices connecting the uppe peripheral edge of the innertank to the outer tank.

Referring now to FIG. 1 there is shown a sectional view of a storagetank according to the invention having a rigid outer tank 1 having apressuretight and hermetically sealed construction and made of steel,designates a heat insulating material having a substantial resistance tocompression such, for example, as a heat insulating layer consisting ofhard polyurethane etc. Inside of this heat insulating layer 2, an innertank 3 is provided. This inner tank 3 is constructed by a thin filmconstruction made of a low-temperature resistant material such asaluminum, nickel steel etc. The inner tank 3 has a sufficientflexibility and is constructed such that when it is subjected to theinner pressure it could not withstand such inner pressure and hence isdeflected towards and brought into close contact with theheat-insulating layer 2, thereby transmitting the inner pressure to thelatter. Therefore, substantially all of the inner pressure is supportedby the rigid outer tank 1 having the pressuretight construction. Theinner tank 3 consists of a flat bottom plate 6 and a cylindrical sideshell connected through a thin film connector construction 5 in theshape of a portion of a toroid to the bottom plate 6. The cylindricalside shell plate is provided with vertically extending corrugations 4which permits the cylindrical side shell plate to expand and contractin' the peripheral direction thereof. 7 shows a top cover constructionof the other tank 1 and 8 a truss for supporting the top cover-plate 7.9 shows a balancing weight device that suspends the upper peripheraledge of the inner tank 3 and moves downward when the lowtemperatureliquefied gas is charged in the inner tank 3 to compensate for thecontraction of the side shell of the inner tank 3. l0 designates a topcover for the inner tank, which is constructed by a thin plate made ofAl, Ni-steel etc. and whose outer peripheral edge in opposition with theinner tank 3 is bent downwards to form a small gap therebetween. llillustrates a heat-insulating material which is not required to be of acompression resisting type and is made for example of glass wool etc. 12designates a member made of wood etc. and adapted to support the topcover 10 of the inner tank 3 an connect the top cover 10 to the truss 8.

Various types of the devices for suspending the upper peripheral edge ofthe inner tank 3 may be constructed and embodiments thereof will now beexplained with reference to FIGS. 68.

In the embodiment shown in FIG. 6 the upper peripheral edge 13 of theinner tank 3 is pivoted to one end of a rocking lever l4 arranged on thetop cover 10 and pivoted to it. The rocking lever 14 is provided at itsopposite end with a weight 15 which is always in balance with that endwhich suspends the upper peripheral edge 13 of the inner tank 3.

In another embodiment shown in FIG. 7 the upper peripheral edge 13 ofthe inner tank 3 is'suspended through a spring or bellows 16 from thetop cover construction 7 of th outer tank 1.

In a further embodiment shown in FIG. 8 the upper peripheral edge 13 ofthe inner tank 3 is suspended through a wire and a pulley 17 from thetop cover construction 7 of the outer tank 1 and always in balance witha weight 18 acting upon the pulley 17. All of these embodiments providemeans for freely following the load produced by the low-temperatureliquefied gas charged in the inner tank 3 and hence follow thedisplacement of the upper peripheral edge 13 of the inner tank 3.

The above-mentioned construction according to the invention in which theinner tank 3 is made of the thin film renders it possible to bring theinner tank 3 into a close contact with the heat-insulating layer 3 bymeans of the inner pressure produced by the low-temperature liquefiedgas charged in the inner tank 3 thus transmitting the inner pressure tothe heatinsulating layer 2, with the result that the outer tank 1 canwithstand the above-mentioned inner pressure and hence can store thelow-temperature liquefied gas in a safe manner. How

to compensate for the deflection of the inner tank 3 caused by theabovesmentioned inner pressure and the contraction of the inner tank 3caused by the low-temperature liquefied gas will now be described.

As shown in FIG. 2, the bottom plate 6 when exposed to the lowtemperature becomes contracted towards the center thereof so that ademarcation line cd located at room temperature between the connectorconstruction 5 and the bottom plate 6 of the inner tank 3 is displacedto dotted lines c'd and hence a demarcation line ab located at roomtemperature between the side shell 3 and the connector construction 5 isdisplaced to dotted lines a'b, thus moving the side shell 3 downwards.Such downward movement of the side shell 3 is capable of compensatingfor the contraction of the bottom plate 6. FIG. 3 diagrammaticallyillustrates the contraction of the inner tank 3 shown in vertical crosssection. As seen from FIG. 3 the inner tank 3 takes a sectional formshown by a full line ac at room temperature under no load condition. Thebottom plate 6 when exposed at the low temperature under the no loadcondition is contracted towards its center to displace a point cto apoint c. The contraction of the side shell reduces the diameter of theinner tank 3 and hence displaces a point a to a point a, with the resultthat a full line ac is displaced to dotted lines ac. The liquid loadapplied to the inner tank 3 having the thin film structure tends to theinner tank 3 to deflect and bring it into a close contact with theheatinsulating layer 2, thereby tending to displace the dotted linesa'-c to the original full line ac. In this case the contraction of thebottom plate 6 from the point c to the point c and the contraction ofthe side shell plate 3 from the point a to the point a tend to bringback the point a to the point b instead of bringing back the point a' tothe point b instead of bringing back the point a to the point a. As seenfrom the above description the deflection of the inner tank 3 caused bythe liquid load at the low temperature consists of a longitudinalcontractive displacement represented by the movement of the point a tothe point b, a peripheral expansion of the side shell 3 from the dottedlines a-c under no load condition to the full line bc under loadedcondition, and a change of curvature of the connector construction 5.The longitudinal contractive displacement can freely be carried out withthe aid of the balancing weight device 9 suspending the upper peripheraledge 13 of the inner tank 3, while the peripheral expansion of the sideshell plate can be carried out by deformation of the longitudinalcorrugations 4. Such deformation of the corrugations 4 is illustrated inFIG. 4-A in which a full line shows the state of the shell 3 in sectionat room temperature under no load condition and dotted lines show howthe side shell 3 deforms at the low temperature under load condition.The corrugations 4 become expanded by the presence of the innerpressure.

As seen from FIG. 4-A points d, e and f are displaced to points d, e and1", respectively, and the distance between the points e and f is reducedby contraction to that between the points e and f. The deformation ofthe corrugations 4 causes the distance between the points d and e toincrease to that between the points d and e. Thus, the elongationbetween the points d and e compensates for the contraction between thepoints 2 and f thus bringing the side shell plate 3 into contact withthe heat insulating wall 2. The corrugations 4 are liable to be easilydeformed by an extremely small force so that dangerous. thermal stressis not produced in the side shell 3. FIG. 4-8 shows a variant of thecorrugations 4 shown in FIG. 4 -A in which corrugations 4 are differentin shape from the corrugations 4 shown in FIG. 4-A. In the presentembodiment the corrugations 4 constitute a camber of a plate. Thiscamber is eliminated by contraction of the side shell 3 at the lowtemperature to deform the side shell 3 into a circular form withoutundulations in section, thereby bringing it into a close contact withthe inside surface of the heat-insulating layer 2. Thus, thecorrugations herein described also means the above mentioned camber.

The inner tank 3 is constructed by a thin film and the corrugationsterminate smoothly at the neighborhood of the connector construction 5so that the curvature of the connector construction 5 can be changedwithout difficulty. Such change of the curvature of the connectorconstruction 5 may more easily be carried out by provision of additionalcorrugations (not shown) along the periphery of the connectorconstruction 5. Thus, the inner tank according to the invention can beeasily deformed in response to the load and the contraction phenomenondue to the low temperature and thereby reduces crack and damages of thetank and stores the low-temperature liquefied gases in a safe manner.

The downwards bent peripheral edge of the top cover 10 of the inner tank3 prevents the low-temperature liquefied gas from flowing out of theinner tank 3 even when the level of the lowtemperature liquefied gasabruptly changes owing to earthquake or other causes. The small gapformed between the downwards bent peripheral edge of the top cover 10and the upper peripheral edge 13 of the inner tank 3 serves to allowcommunication between inside and outside of the inner tank 3 and hencepassage of vapor.

That part of the vapor which makes contact with the inside surface ofthe outer tank 1 which is commonly made of steel plate, is heated toambient temperature so that the outer tank is not liable to be brittleand hence damaged owing to the low temperature.

The space formed between the inner and outer tanks is filled with vaporso that frost and ice etc. do not occur at those portions which arepositioned in this space without necessitating any means of drying thespace formed between the inner and outer tanks, as in double-walledtanks heretofore proposed.

It will be seen that the storage tanks according to the invention aresimple and economical to construct, and result in a considerable safetyin the storage of the low-temperature liquefied gases.

It is to be understood that the forms of the invention herewith shownand described are to be as preferred examples of the same, and thatvarious changes in the shape, size and arrangement of the parts may beresorted to without departing from the spirit of the invention or thescope of the subjoined claims.

We claim:

1. A liquefied gas storage tank comprising, in combination, an outertank having a pressure tight and hermetically sealed rigid construction,a heat-insulating layer having a substantial resistance to compressionand provided at the inside surface of at least side and bottom portionsof said outer tank, a top closure structure provided on said outer tank,an inner tank having a thin wall construction located inwardly of saidheat insulating layer and adapted to contain a low-temperature liquefiedgas therein, the pressure of said liquefied gas being supported throughsaid inner tank and heat insulating layer by said outer tank, said innertank being formed into a bagshaped body consisting of a flat bottomplate and a cylindrical side shell connected at its bottom edge to saidflat bottom plate by a thin film connector construction in the shape ofa portion of a toroid. Said side shell including an upper, peripheraledge defining an upper opening, movable suspension means connecting saidupper peripheral edge of said bagshaped inner tank to said top closurestructure of said outer tank, said upper opening of said inner tankbeing covered by a top cover plate secured to said top closure structureindependently of said inner tank and provided with a heat-insulatinglayer, and said inner tank having elongated substantially verticalcorrugations arranged in spaced relationship about the periphery of saidside shell, said corrugations extending radially across said connectorconstruction and smoothly reducing in width as they approach said flatbottom plate and smoothly terminating in the area of the junction ofsaid connector constructions to said flat bottom plate.

2. A liquefied gas storage tank as claimed in claim 1 wherein saidsuspension means comprises a plurality of rocking levers tached to saidtop structure and weight means, each of said weight means being attachedto a line,-and each line passing over at least one pulley and connectingto said upper periphery of said inner tank.

5. A liquefied gas storage tank as claimed in claim 1 wherein saidcorrugations are constituted by a slightly curved camber 1 adapted to bedeformed into substantially a circular form in horizontal section uponbeing subjected to a low-temperature liquid load. 1

2. A liquefied gas storage tank as claimed in claim 1 wherein saidsuspension means comprises a plurality of rocking levers pivotablyconnected to said top cover plate, weight means at one end of each ofsaid levers to counterbalance said inner tank, and said upper peripheryof said inner tank being connected to the other ends of said levers. 3.A liquefied gas storage tank as claimed in claim 1 wherein saidsuspension means comprises a plurality of spring means connecting saidupper periphery of said inner tank to said top structure.
 4. A liquefiedgas storage tank as claimed in claim 1 wherein said suspension meanscomprises a plurality of pulleys attached to said top structure andweight means, each of said weight means being attached to a line, andeach line passing over at least one pulley and connecting to said upperperiphery of said inner tank.
 5. A liquefied gas storage tank as claimedin claim 1 wherein said corrugations are constituted by a slightlycurved camber adapted to be deformed into substantially a circular formin horizontal section upon being subjected to a low-temperature liquidload.